Spatial dynamic evolution process of overburden rock mining and coal-based solid waste grouting and filling practice

In the process of mining thick coal seams, the overlying rock layer will undergo a gradual dynamic evolution from local deformation to overall failure under the action of mining stress, and it is easy to form underground spaces such as in-situ goafs, low-level collapse zones, and high-level separation zones, which in turn cause geological problems such as rock stratum movement and surface subsidence. At the same time, the accumulation of coal-based solid waste such as coal gangue generated by coal mining not only occupies land, but also has the risk of environmental pollution, and its disposal demand is highly compatible with the key space formed by the migration of overburden rock from thick coal seam mining. Therefore, this paper systematically studies the dynamic evolution process of the overburden space of thick coal seam mining, and reveals the characteristics of three stages: initial mining, mining development, and mining stability. By analyzing the control mechanism of internal attributes and external factors on the evolution of overburdened rock, the formation mechanism and distribution law of key spaces are clarified, and the differentiated processes of in-situ goaf grouting, low-level collapse zone grouting and high-level separation grouting are proposed, and then a multi-level collaborative grouting and filling system of “lower bearing-middle solid-top control” is constructed. Similar simulation tests were carried out to study the dynamic evolution of key space and grouting filling effect of overburdened rock, and the collapse, fracture development and separation formation process in the dynamic evolution of overburden rock were reproduced, and the control effects of in-situ goaf grouting, low-level collapse zone grouting and high-level separation grouting on the movement of overburden rock were quantitatively analyzed, which provided an experimental basis for theoretical analysis conclusions and optimization of technical parameters. In terms of engineering applications, the grouting in the goaf of Baozigou Coal Mine, the grouting in the rising area of Renjiazhuang Coal Mine and the separation grouting of Huoerxinghe Coal Mine have all realized the large-scale disposal of coal-based solid waste, verified the adaptability of grouting and filling technology system under different geological conditions, and achieved the effect of improving the stability of overburden rock and effectively controlling surface subsidence, providing a generalizable practice example for green mining of thick coal seams. Through the closed-loop verification of theory, experiment and practice, the internal relationship between the evolution of overburden rock in thick coal seam mining and grouting and filling is clarified, and a multi-layer collaborative control technology system for thick coal seam mining is constructed, which provides some theoretical support and technical paradigm for the prevention and control of overburden disasters and the resource utilization of coal-based solid waste in thick coal seam mining.